More than 60 House Democrats have signed a letter asking President Obama to issue an executive order requiring federal contractors to disclose political contributions.

The proposal is one of a handful floated in the wake of the Supreme Court’s landmark Citizens United decision last year, which loosened restrictions on corporate political advocacy.

The letter indicates the strong support among rank-and-file Democratic lawmakers for a measure that has been attacked by Republicans.

“We believe that with public funds come public responsibilities,” the letter reads, “and anyone benefiting from taxpayer money has the responsibility to be fully transparent.”

In April, the White House first circulated a draft of the executive order, which would have required companies bidding on federal contracts to disclose political donations from their corporate coffers and top executives, including contributions to nonprofit advocacy groups that would not otherwise be a part of the public record.

The proposal was opposed by the business community and conservatives, who said it would politicize government contracting by making bureaucrats aware of political spending by bidders.

“If you were to get in a letter writing contest, there would be a lot more signatories asking the president not to finalize the executive order,” said Brad Smith, a co-founder of the Center for Competitive Politics, which opposes the regulation of political money. “It’s an effort to implement the Disclose Act through executive order,” he said, referring to unsuccessful Democratic legislation last year that was designed to force interest groups to reveal the sources of donations made in support of political advertising.

“Disclosure will not politicize the procurement process — it will improve it,” the letter says. “Political expenditures are already well-known to those that make them and to the officials who benefit. With disclosure, the public will have access to this information as well, allowing them to judge whether contracts were awarded based on merit.”

The letter was delivered to the White House on Thursday morning and is signed by 62 House Democrats.

The initial proposal was trumpeted by the White House as a response to the increase in spending ahead of the 2010 midterm elections by political interest groups that are not required to disclose their contributors. Democrats have assailed such spending — which has heavily favored Republican candidates — as potentially corrupting.

Republicans have sponsored several measures that would have prohibited new disclosure requirements, but none of them became law. The order was never signed and has been out of the news for more than a month.

“There is a whole new level, with a tsunami of money that’s washing over the country and our political system,” said Rep. Anna G. Eshoo (D-Calif.), who wrote the letter and collected signatures on the House floor. “I don’t think anyone can say with a straight face, ‘This is a terrific system.’ It just isn’t. When you add to it the Citizens United decision, there is no way that anyone can stand up to those dollars.”